The use of hot wires and hot films as anemometer transducers is well known in the prior art. Examples of prior art thermal anemometer sensors, and circuits therefor, are shown in U.S. Pat. Nos. 3,138,025, 3,333,470, 3,352,154, 3,604,261, 3,900,819 and 4,024,761, as well as in co-pending U.S. patent application Ser. No. 966,792 now U.S. Pat. No. 4,206,638. The present invention provides a significant improvement in the angular response or azimuth response of the transducer as well as a reduction in the excitation power which is needed to arrive at a useful operating sensitivity level.
Prior art transducers, which use no moving parts, have characteristically had some degree of difficulty in realizing a smooth and continuous transition from one direction to the opposite direction. The use of electrical "dither" signals and artificial "lobe switching" from side to side has helped to reduce axis crossing irregularities. Further improvement has been brought about by the use of a self-induced turbulent wake as a naturally occurring "dither" signal in the axis crossing regions.